The embryos from Florida and Mexico developed similarly in the first 50 hours, with the high-temperature embryos maturing only slightly faster than the embryos raised at normal temperatures. Strikingly, larvae raised at higher temperatures showed many more irregular, misshapen embryos than those raised at normal temperatures. For example, after 46 hours, fully 50 percent of the high-temperature embryos from Florida were deformed as compared to the normal-temperature embryos, none of which were malformed. The Mexican samples showed the same pattern but those embryos were less strongly affected by the elevated temperature. Although both populations represent the same species, they responded differently to heat stress, showing genetic variability within the species.
In addition to examining the physical appearance of embryos as they developed, the team extracted RNA from approximately 1,500 embryos from each location to see how much of each of 1,300 molecular products were being transcribed at a given time. Genes that were transcribed in different amounts between high-temperature and normal-temperature samples were called deferentially expressed genes. Twenty-four hours after fertilization, embryos from the same site showed similar gene expression profiles regardless of the temperature at which they were raised. As the time since fertilization increased, the samples showed more and more deferentially expressed genes, 458 in all. Of the 218 deferentially expressed genes that were sensitive to temperature, almost none were shared between the two locations on the first day of sampling, but by the second day, roughly 25 percent were shared between samples from Mexico and Florida. By 48 hours, thermal stress -- not sampling location -- became the dominant factor influencing gene expression. At that point, the gene expression of coral subjected to similar temperatures clustered together regardles
|Contact: Barbara K. Kennedy|